Skip to main content

m/s decoder

Member for

15 years 3 months
sorry to repeat this question from another thread, but i'd really like to know...

is there any stand alone m/s encoder in the market? a web search reveals nothing other than mic preamps and portable recorders with built in encoders...

thanks,

Comments

Member for

16 years 5 months

Zilla Wed, 02/14/2007 - 13:25
DavidSpearritt wrote: Because sound hits your mikes on-axis with M/S. ... tonal improvements are significant.
The sound source can only be on-axis with one mic (M), and only when the primary sound source is dead in the center (ex: a soloist). True, there can be a tonal improvement in some situations, and hopefully one that overcomes the potential coloring of the decoding process. For fun, one could argue that with larger ensembles an x-y array has more information on-axis than a m/s (ex: center main pair of an orchestra 4-way). But making such an arguement would only peg me as an audio nerd, so l will skip it.

Member for

15 years 4 months

Boswell Wed, 02/14/2007 - 15:43
Zilla wrote: If all your going to do is decode to x-y, why not just use x-y technique in the first place?
M-S sounds different from X-Y on most sources. Not always better, but different. It is another option in the recording engineer's array of options. But it's surprising how often you turn to M-S when faced with a "now how shall I try miking this up?" situation.
You may need to take care with what that circuit is connected to. The following device will be loading that network. Transformers are reactive components. That means that it will react differently depending on signal frequency. Loading (terminating) the transformer with a proper Z will optimize linear response in the audio band.
This is specifically a headphone monitoring decoder circuit. The specified transformer is designed for headphone power levels. It's driven from a headphone amplifier and is loaded by the impedance of the headphones. The 15 Ohm resistor compensates the M-channel for the resistive losses of the transformer primary in the S-channel.
I don't care much for this circuit because it has no control of mid-side balance. To me, that is the whole advantage of the technique: flexibility.
This circuit is for monitoring M-S encoded channels as they are being recorded still in their encoded form. You adjust the M-S balance (and hence the L-R width) at mixdown. At that stage, you use a separate decoding matrix, not this headphone decoder, between the M-S inputs and the L-R stereo mix bus. For a two-channel recording, the mixdown may simply consist of M-S level adjust followed by decode to L-R, but that is just a trivial case of a multi-track recording.

Member for

16 years 8 months

mdemeyer Wed, 02/14/2007 - 16:51
Yes, that's the transformer I used. When I got them I had to wait for shipment from UK, but the US importer told me he would stock a few.

The circuit is that simple and, in my experience with a variety of headphones and driving sources, works fine.

Regarding M/S balance, you just adjust the feeds to the transformer. Works fine.

Michael

Member for

16 years 5 months

Zilla Wed, 02/14/2007 - 17:44
Boswell wrote: M-S sounds different from X-Y on most sources. Not always better, but different. It is another option in the recording engineer's array of options.
Fair enough.
Boswell wrote: The specified transformer is designed for headphone power levels. It's driven from a headphone amplifier and is loaded by the impedance of the headphones.
Headphone Z does vary across makes and models. A 30ohm HP will load those xfrmrs differently than a 600ohm pair. It would be interesting to see if it made any appreciable difference in response. I would imagine that the manufacture's design would have made allowances for this.
Boswell wrote: This circuit is for monitoring M-S encoded channels as they are being recorded ... adjust the M-S balance...at mixdown.
Yes, this would function and get you through the session. For me, it is not an ideal solution. Being able to monitor the decoded signal better informs the engineer and helps optimize mic placement. It allows the engineer to 'play' with the interaction between m/s width and mic placement. I guess I am just uncomfortable with waiting for post-production to hear the what the possibilities might be.

Member for

15 years 3 months

rfreez Wed, 02/14/2007 - 23:27
sorry to go off topic, but,

from the first page of the mr-1000 instruction manual:

Using the unit in the following locations can result in a malfunction.

• In direct sunlight
• Locations of extreme temperature or humidity
• Excessively dusty or dirty
• Locations of excessive vibration
• Close to magnetic fields

is this a location recorder or what? :roll:

this is what the sound devices manual says:

The 702 output meter is unaffected by shock or extremes in temperature and humidity.


and either the instruction manual is woefully incomplete or the damn thing doesn't even allow you to adjust the balance between, and levels of the two inputs, for the headphone output :shock:

what simmo said about the unit being a toy is becoming more and more apparent...

Member for

15 years 4 months

Boswell Thu, 02/15/2007 - 02:41
rfreez wrote: either the instruction manual is woefully incomplete or the damn thing doesn't even allow you to adjust the balance between, and levels of the two inputs, for the headphone output :shock:
Yes, I think the headphone monitor feels a bit of a bolt-on. It's got a control marked "volume" and nothing else. Bear in mind, though, that the unit is basically a two-track recorder, and the live headphone monitoring is a check that you are recording something on each of the two tracks, not an emulation of studio monitoring during post processing.

Given the necessary limitations of the unit, I think the transformer M-S decoder for the headphone channel is a good solution, affording you the choice of L-R (in its various forms) or M-S miking in the field. You could house the transformer in a convenient lump in an adaptor cord along with a TRS jack socket and a by-pass switch. The other end of the cord would have the TRS jack plug to mate with the regular headphone output on the MR-1000. The switch avoids the need to keep plugging and unplugging the adaptor cable when listening to replays of L-R and M-S recorded tracks.

Member for

16 years 8 months

DavidSpearritt Thu, 02/15/2007 - 09:58
Zilla wrote: [quote=DavidSpearritt]Because sound hits your mikes on-axis with M/S. ... tonal improvements are significant.
The sound source can only be on-axis with one mic (M), and only when the primary sound source is dead in the center (ex: a soloist). True, there can be a tonal improvement in some situations, and hopefully one that overcomes the potential coloring of the decoding process. For fun, one could argue that with larger ensembles an x-y array has more information on-axis than a m/s (ex: center main pair of an orchestra 4-way). But making such an arguement would only peg me as an audio nerd, so l will skip it.
Two counter points, a fig 8 has much better off axis tonality than a cardioid, so the side mic sounds much better than another card, giving both mics of an MS pair significantly better tonal response to any off axis sounds.

MS shouldn't and isn't used for big sources by those in the know. Its best for small ensembles that fit into about 90 deg or less. For large sources a couple of omnis starts to work well.

Member for

16 years 5 months

Zilla Thu, 02/15/2007 - 10:54
Two good points. Generally bi-directional mics do have smoother off-axis response. The question is does a given bi-directional mic have an over-all preferable sound than a given cardioid. The choice is completely dependent on situation and taste.

I agree with you that coincident mic technics (x-y, m/s) are most appropriate for small ensembles. However, there are a number of professional engineers out there who indeed employee m/s on orchestra's, opera and other large ensembles. The sonics are not my cup of tea, but the record sales obviously show that it can be successful.

Member for

16 years 8 months

Simmosonic Fri, 02/16/2007 - 03:46
Boswell wrote: Given the necessary limitations of the unit, I think the transformer M-S decoder for the headphone channel is a good solution, affording you the choice of L-R (in its various forms) or M-S miking in the field.

There may be a problem here that we have not considered because the Sowter, like other transformer decoders, is a passive device and therefore will incur an insertion loss of power. This could be a bad thing when driving it from the headphone output of the Korg, which is ultimately a low-voltage battery-powered device and can therefore only produce a relatively small output voltage swing (compared to a mains-powered device with supply rails of +/-15V or more). To get more power into the headphones requires drawing more output current, and that in turn requires lower impedance headphones.

This is particularly important in situations where it is necessary to monitor the recording while in the same space as the performers, because, with such a decoding circuit in place, it may be impossible to drive the headphones to a sufficient SPL for meaningful monitoring without clipping.

Although I was one of the supporters of the transformer solution, I was not thinking of the Korg's headphone driving capability at the time. I suspect an active device that decodes MS and drives headphones may be more appropriate. Or better yet, ditch the Korg and go with the SD!

Member for

15 years 11 months

aracu Fri, 02/16/2007 - 09:22
"The SD 744T has two built-in M-S decoders, one switchable to operate on channels 1 & 2 as a pair, and the other in the headphone output. So you can use a single M-S pair and two other mono mics and record 4 channels of decoded signals, using conventional headphone monitoring. OR, you can have two pairs of M-S mics and record them as M-S channels, using the headphone M-S decoder for monitoring. This may be what you want to do, but I'm not clear."

Boswell, thanks for taking the effort to answer my question.
I noticed that with the 744t, you can monitor an ms pair through
the headphone output without processing the signal. So what I
was wondering was if there were a cost effective way of monitering
2 ms pairs without processing (those 4 channels divided into two
separate pairs of ms). An expensive way to do it would be to use
2 Sound Devices recorders and combine the headphone outputs
to stereo. It's possible that there isn't a simple way of doing it due
of the nature of standard ms matrixes.

Reme, I am not impressed by your condescending attitude,
which has already been commented on in these forums.

Member for

15 years 4 months

Boswell Fri, 02/16/2007 - 11:29
aracu wrote: "The SD 744T has two built-in M-S decoders, one switchable to operate on channels 1 & 2 as a pair, and the other in the headphone output. So you can use a single M-S pair and two other mono mics and record 4 channels of decoded signals, using conventional headphone monitoring. OR, you can have two pairs of M-S mics and record them as M-S channels, using the headphone M-S decoder for monitoring. This may be what you want to do, but I'm not clear."

Boswell, thanks for taking the effort to answer my question.
I noticed that with the 744t, you can monitor an ms pair through
the headphone output without processing the signal. So what I
was wondering was if there were a cost effective way of monitering
2 ms pairs without processing (those 4 channels divided into two
separate pairs of ms). An expensive way to do it would be to use
2 Sound Devices recorders and combine the headphone outputs
to stereo. It's possible that there isn't a simple way of doing it due
of the nature of standard ms matrixes.
I haven't got the 744T manual to hand, but my memory of how the headphone monitor works is that you have 20+ options to choose from, including having two M-S pairs as the four channels and alternating the monitoring between the two pairs. If you want to hear the summed L and R from the decoded M-S pairs, I think you're out of luck using the options available on the machine. However, if you were to select "Monitor 1+3, 2+4", you could get encoded M-S summed channels at the headphone jack, so an external transformer-based MS decoder would give you an L-R pair. Quite what that would mean as a sound field would depend entirely on your microphone placement, but presumably that would be your intention for post processing anyway.
x